Conventionally, an air conditioner for a vehicle, described in Patent Document 1 (JP 3750255 B2), is known. The air conditioner includes an electric heater as an auxiliary heater, which is arranged between a heating heat exchanger and a foot air outlet to compensate for a lack of heating capacity of the air conditioner.
The air conditioner can be set in an inside-outside air double-layer mode, in which inside air and outside air flow separately inside the air conditioner. The electric heater is arranged in a space where the inside air flows in the double-layer mode.
When a maximum heating (MAX-HOT) operation is performed, all amount of air to be blown out of the air conditioner may be heated in the electric heater. However, when a heating operation other than the maximum heating operation is performed, the air heated in the electric heater may be mixed with cool air not-heated by the electric heater.
Hence, the air mixed with cool air may be blown to a driver just entered into a vehicle compartment of the vehicle from cold outside. In this case, a capacity of the air conditioner to heat the driver may be reduced. Therefore, a vehicle air conditioner is required, which is capable of effectively performing an effective immediate heating operation in accordance with a requirement of a driver even when it is unnecessary to perform a maximum heating for a vehicle compartment.